1. Field of the Invention
This invention relates to an optical information recording and reproducing method and device, and more particularly, to an optical information recording and reproducing method and device, whereby improvement can be made in the performance of track jump operations of a light beam spot to a desired information track on a card-shaped optical recording medium, whereon a plurality of information tracks are formed mutually in parallel.
2. Description of the Related Art
In many optical information recording and reproduction devices, whereby information is recorded onto and reproduced from an optical information recording medium whilst causing the recording medium to move at high speed relative to an optical head emitting a light beam spot, a card-shaped recording medium, in other words, a recording medium called an optical card, is used.
Here, FIG. 6 shows the composition of a general optical card.
As FIG. 6 shows, the optical card 500 comprises several thousand or several ten thousand information tracks 504 formed mutually in parallel in an information recording region 501 thereof, and information is recorded by shining a light beam spot onto the central region 502 (region represented by p.times.q surface area) of these information tracks 504 to form pits, and information is reproduced by detecting the presence or absence of pits from the reflected light of the light beam spot.
In addition to forming pits when recording information on the central region 502, pre-formatted information, such as address information for specifying data groups or information tracks 504 required for acquiring bit synchronization, is recorded previously by creating pits.
On the other hand, the end regions 503 (regions represented by r.times.q surface area) of the information tracks 504 are regions for accelerating and decelerating in order that the optical card is moved at a constant speed relative to the optical head, so no pits are formed in these regions.
FIG. 7 is a diagram giving a partial enlarged illustration of the information recording region 501 of the optical card 500.
Information tracks 504 (504-1, 504-2, 504-3) and guide tracks 505 (505-1-505-4) are formed on the information recording region 501, and pre-formatted data pits 506 constituting pre-formatted data, such as address information, and the like, and recording pits 507 constituting data recorded by the user are formed on the information tracks 504, the absence or presence or these pre-formatted data pits 506 or recording pits 507 representing the respective data types.
The guide tracks 505 are regions of different reflectivity to the information tracks 504, and they are used for autotracking (hereinafter, abbreviated as AT) control in order that the optical information recording and reproduction device does not deviate from the information track 504 when scanning a desired information track 504.
FIG. 8 is a block diagram showing the composition of an optical information recording and reproduction device, and FIG. 9 is an approximate diagram showing the composition of an optical head.
In FIG. 8, the optical information recording and reproduction device 510 comprises: a CPU (Central Processing Unit) 511 for overall control of the device; an MPU (Microprocessor Unit) 512 for controlling the section relating to the recording and reproduction operations of the device, on the basis of the control implemented by the CPU 511; a modulating and demodulating circuit 513 for modulating data being recorded and demodulating data being reproduced; an optical head 514 for creating and detecting recording pits 507, and the like; a y-direction drive motor 515 which drives the optical head 514 reciprocally in the y direction; an x-direction drive motor 516 which drives the optical card 500 reciprocally in the x direction; a track jump circuit 517 for controlling track jumping; an AF/AT control circuit 518 for performing autofocussing (hereinafter, abbreviated as AF) control and AT control such that a focused light beam spot is shined onto the surface of the light card 500 at all times, even if there are fluctuation in this surface; and a movement speed detecting circuit 519 for detecting the speed of movement of the optical card 500.
Furthermore, as shown in FIG. 9, the optical head 514 comprises: a semiconductor laser 541, collimator lens 542, diffraction grating 543, beam splitter 544, object lens 545, light receiving lens 546, photoreceptor 547, and actuator 548. Laser light output from the semiconductor laser 541 is formed into parallel light by the collimator lens 542 and split by the diffraction grating 543 into three beams, which are shined via the beam splitter 544 and object lens 545 onto the optical card 500 as beam spots 550. The reflected light from the beam spots 550 shined onto the optical card 500 passes through the object lens 545, beam splitter 544 and light receiving lens 546 and is converted to an electrical signal by the photoreceptor 547. Since one of the three beam spots shined onto the optical card 500 is shined onto an information track 504, and the other two beam spots are shined onto the guide tracks 505 on either side of this information track 504, the reflected light, in other words, the signal converted to an electrical signal by the photoreceptor 547, contains a focussing control signal and tracking control signal in addition to a data signal. In order for the optical recording and reproduction device 510 to record or reproduce information on a desired information track 504, the information track 504 must be selected accurately. In general, the operation of selecting an information track is call track access, or simply access, and it comprises the operations of moving the whole optical head 514 in a direction perpendicular to the information track 504, and moving a portion of the optical system in the optical head 514, for instance, the object lens 545, in a direction perpendicular to the information tracks 504 by means of an actuator 548, the latter operation also being called a track jump operation.
Here, a first example relating to a conventional track jump operation, wherein the relative speed of movement between the optical card and optical head is constant, is described with reference to FIG. 10 and FIG. 11.
FIG. 10 is a diagram illustrating the relationship between the relative speed of movement of the optical card and time, and their relationship to the pulse voltage applied by the optical information recording and reproduction device to the actuator for moving the optical card and time. FIG. 11 is a flowchart showing the sequence of a track jump operation in an optical information recording and reproduction device.
In order to record or reproduce information to or from the optical card, the optical recording and reproduction device 510 starts an operation whereby the optical card 500 is moved reciprocally by driving the x direction drive motor 516, such that the optical card 500 and optical head 514 move relative to each other (step 601 in FIG. 11), and the MPU 512 applies an acceleration pulse (voltage V1) to the x direction drive motor 516 to accelerate the relative speed of movement of the optical card 500 to a prescribed speed v1 (step 602; section a in FIG. 10).
If the movement speed detecting circuit 519 detects that the relative speed of movement of the optical card 500 has reached a prescribed speed v1, (hereinafter, all detection of the relative speed of movement of the optical card 500 is carried out by the movement speed detecting circuit 519), then the optical recording and reproduction device 510 applies a constant-speed pulse (voltage V2) for maintaining that speed to the x direction drive motor 516 (step 603; section b), and performs a recording operation for recording information modulated by the modulating and demodulating circuit 513 onto a prescribed information track 504 of the optical card 500, or a reproduction operation for reproducing information recorded on a prescribed information track 504 of the optical card 500 and demodulating the information by means of the modulating and demodulating circuit 513, in a state where the relative speed of movement of the optical card 500 is constant (step 604; section b).
When the recording or reproduction operation is completed, the optical information recording and reproduction device 510 actuates the AF/AT control circuit 518, opening the AT control loop and halting AT control, (step 605, section b), whilst maintaining the relative speed of movement of the optical card 500 at v1.
The AT control is halted in this way because the object of AT control is to make the light beam spot continue shining on the desired information track, and therefore when performing a track jump for moving the light beam spot to a different information track 504, the AT control and track jump operations conflict with each other.
When the AT control is halted, the track jump circuit 517 applies a track jump pulse to the actuator 548 which moves the object lens 545, thereby causing the object lens 545 to move in a direction perpendicular to the information tracks 504 (step 606; section b).
Thereupon, the track jump circuit 517 applies a brake pulse of opposite polarity to the track jump pulse to the actuator 548, (step 607, section b), thereby decelerating the speed of movement of the object lens 545 and causing the object lens 545 to come to rest in a position whereby the light beam spot shines on the desired information track 504.
When the point of illumination of the light beam spot moves to the desired information track 504, the AF/AT control circuit 518 closes the AT control loop and starts AT control (step S608, section b), and the MPU 512 applies a decelerating pulse (voltage -V1) to the x direction drive motor 516, thereby decelerating the relative speed of movement of the optical card 500 (step 609, section c). This decelerating pulse is applied until the relative speed of movement of the optical card 500 reaches zero (NO at step 610), and when this relative speed of movement reaches zero (YES at step 610, section d), an accelerating pulse (voltage -V1) is applied to the x direction drive motor 516 and the relative speed of movement of the optical card 500 is accelerated until it reaches a prescribed speed -v1 (step 611, section e). Here, the accelerating pulse applied is an accelerating pulse of opposite polarity to the accelerating pulse applied at step 602, and therefore the direction of the relative movement of the optical card 500 is opposite to the direction of movement when in the acceleration operation in step 602.
When the relative speed of movement of the optical card 500 reaches a prescribed speed -v1, the MPU 512 applies a constant-speed pulse (voltage -V1) for maintaining that speed to the x direction drive motor 516 (step 612, section f), and the optical head 514 records or reproduces information to or form a desired information track 504 of the optical card 500 (step 613, section f), whereupon the AF/AT control circuit 518 closes the AT control loop and halts AT control (step 614, section f).
When the AT control is halted, the track jump circuit 517 applies a track jump pulse to the actuator 548, thereby causing the object lens 545 to move in the direction perpendicular to the information tracks 504 (step 615, section f).
Thereupon, the track jump circuit 517 applies a brake pulse of opposite polarity to the track jump pulse to the actuator 548 (step 616, section f), thereby decelerating the speed of movement of the object lens 545 and causing the object lens 545 to come to rest in a position whereby the light beam spot shines onto the desired information track 504.
When the point of illumination of the light beam spot has moved to the desired information track 504, the AF/AT control circuit 518 closes the AT control loop and starts AT control (step 617, section f).
Next, the MPU 512 applies a decelerating pulse (voltage V1) to the x direction drive motor 516, decelerating the relative speed of movement of the optical card (step 618, section g), and when the relative speed of movement reaches zero (YES at step 619, section h), the process returns to step 602 and an accelerating pulse is applied again to the x direction drive motor 516 (step 602, section i).
These operations are repeated until the optical recording and reproduction device 510 has completed the prescribed recording or reproduction operation.
Next, a case where a track jump operation is carried out in a state where the relative speed of movement between the optical card and optical head is zero, as proposed in Japanese Patent Examined Publication No. 6-9088, is described with reference to FIG. 10 and FIG. 12, as a second example of a conventional track jump operation.
FIG. 12 is a flowchart showing the sequence of a track jump operation in an optical recording and reproduction device.
When the optical recording and reproduction device 510 starts an operation whereby the optical card 500 and optical head 514 are moved relative to each other by moving the optical card 500 reciprocally, in order to record and reproduce information to and from the optical card 500, (step 701 in FIG. 12), the MPU 512 applies an accelerating pulse (voltage V1) to the x direction drive motor 516, thereby accelerating the speed of relative movement of the optical card 500 to a prescribed speed v1 (step 702; section a in FIG. 10).
When the relative speed of movement of the optical card 505505 reaches the prescribed speed v1, the MPU 512 applies a constant-speed pulse (voltage V2) for maintaining that speed to the x direction drive motor 516 (step 703, section b), and the optical head 514 records or reproduces information to or from a prescribed information track 504 of the optical card 500 (step 704, section b).
When the optical card 500 and optical head 514 assume a prescribed positional relationship, the MPU 512 applies a decelerating pulse (voltage -V1) to the x direction drive motor 516, thereby decelerating the relative speed of movement of the optical card 500 (step 705, section c). This decelerating pulse is applied until the relative speed of movement of the optical card 500 reaches zero (NO at step 706), and when the relative speed of movement reaches zero (YES at step 706, section d), the AF/AT control circuit 518 opens the AT control loop and halts AT control (step 707, section d).
When the AT control is halted, the track jump circuit 517 applies a track jump pulse to the actuator 548 which drives the object lens 545, thereby moving the object lens 545 in a direction perpendicular to the information track 504 (step 708, section d).
Next, the track jump circuit 517 applies a brake pulse of opposite polarity to the track jump pulse to the actuator 548 (step 709, section d), thereby decelerating the speed of movement of the object lens 545, such that the object lens comes to rest in a position where the light beam spot shines onto the desired information track 504.
When the illumination point of the light beam spot has moved to the desired information track 504, the AF/AT control circuit 518 closes the AT control loop and starts AT control (step 710, section d), and the MPU 512 applies an accelerating pulse (voltage -V1) to the x direction drive motor 516, thereby accelerating the relative speed of movement of the optical card 500 to the prescribed speed-v1(step 711, section e). Here, the accelerating pulse applied is of opposite polarity to the accelerating pulse applied at step 702, and the direction of relative movement of the optical card 500 is opposite to the direction of movement due to the acceleration in step 702.
When the relative speed of movement of the optical card 500 has reached a prescribed speed-v1, the MPU 512 applies a constant-speed pulse (voltage-v2) for maintaining this speed to the x direction drive motor 516 (step 712, section f), and the optical head 514 records or reproduces information to or from a desired information track 504 of the optical card 500 (step 713, section f).
When the optical card 500 and optical head 514 assume a prescribed positional relationship, the MPU 512 applies a decelerating pulse (voltage V1) to the x direction drive motor 516, decelerating the relative speed of movement of the optical card 500 (step 714, section g), and when the relative speed of movement reaches zero (YES at step 715, section h), the AF/AT control circuit 518 opens the AT control loop and halts AT control (step 716, section h).
When the AT control is halted, the track jump circuit 517 applies a jump track pulse to the actuator 548, thereby causing the object lens 545 to move in a direction perpendicular to the information tracks 504 (step 717, section h).
Next, the track jump circuit 517 applies a brake pulse of opposite polarity to the track jump pulse to the actuator 548 (step 718, section h), decelerating the speed of movement of the object lens 545 such that it comes to rest in a position where the light beam spot is shined onto the desired information track 504.
When the illumination point of the light beam spot has moved to the desired information track 504, the AF/AT control circuit 518 closes the AT control loop and starts AT control (step 719, section h), and the process returns to step 702, where the MPU 512 applies an accelerating pulse to the x direction drive motor 516 (step 702, section i).
These operations are repeated until the optical recording and reproduction device 510 has completed the prescribed recording and reproduction operations.
Next, a case where a track jump operation is implemented when the relative speed of movement between the optical card and optical head is accelerating or decelerating, as disclosed in Japanese Patent Unexamined Publication No. 5-282682, is described with reference to FIG. 10 and FIG. 13 as a third example of a conventional track jump operation.
FIG. 13 is a flowchart showing the sequence of a track jump operation in an optical recording and reproduction device.
When an operation is started whereby the optical card 500 and optical head 514 are moved relative to each other by moving the optical card 500 reciprocally, in order that the optical recording and reproduction device 510 records or reproduces information to or from the optical card 500 (step 801 in FIG. 13), the MPU 512 applies an accelerating pulse (voltage V1) to the x direction drive motor and accelerates the relative speed of movement of the optical card 500 to a prescribed speed v1 (step 802, section a in FIG. 10).
Here, in the period until the relative speed of movement of the optical card 500 reaches the speed v1, the AF/AT control circuit 518 opens the AT control loop and halts AT control (step 803, section a), and the track jump circuit 517 applies a track jump pulse to the actuator 548, causing the object lens 545 to move in a direction perpendicular to the information tracks 504 (step 804, section a).
Thereupon, the track jump circuit 517 applies a brake pulse of opposite polarity to the track jump pulse to the actuator 548 (step 805, section a), thereby decelerating the speed of movement of the object lens 545 such that it comes to rest in a position where the light beam spot shines onto the desired information track 504.
When the illumination point of the light beam spot has moved to the desired information track 504, the AF/AT control circuit 518 closes the AT control loop and starts AT control (step 806, section a).
Next, when the relative speed of movement of the optical card 500 reaches the prescribed speed v1, the MPU 512 applies a constant-speed pulse (voltage V2) for maintaining this speed to the x direction drive motor 516 (step 807, section b), and the optical head 514 records or reproduces information to or from a desired track 504 of the optical card 500 (step 807, section b).
When the optical card 500 and optical head 514 assume a prescribed positional relationship, the MPU 512 applies a decelerating pulse (voltage -V1) to the x direction drive motor 516, thereby decelerating the relative speed of movement of the optical card 500 (step 809, section c). This decelerating pulse is applied until the relative speed of movement of the optical card 500 reaches zero (NO at step 810), and when the relative speed of movement reaches zero (YES at step 810, section d), the MPU 512 applies an accelerating pulse (voltage -V1) to the x direction drive motor 516, accelerating the relative speed of movement of the optical card 500 to a prescribed speed-v1 (step 811, section e).
In this case, the accelerating pulse applied is of opposite polarity to the accelerating pulse applied in step 802, and the direction of relative movement of the optical card 500 is opposite to the direction of movement inducted by the acceleration in step 802.
Here, in the period until the relative speed of movement of the optical card 500 reaches the speed-v1, the AF/AT control circuit 518 opens the AT control loop and halts AT control (step 812, section e), and the track jump circuit 517 applies a track jump pulse to the actuator 548, causing the object lens 545 to move in a direction perpendicular to the information tracks 504 (step 813, section e).
Thereupon, the track jump circuit 517 applies a brake pulse of opposite polarity to the track jump pulse to the actuator 548 (step 814, section e), thereby decelerating the speed of movement of the object lens 545 such that it comes to rest in a position where the light beam spot shines onto the desired information track 504.
When the illumination point of the light beam spot has moved to the desired information track 504, the AF/AT control circuit 518 closes the AT control loop and starts AT control (step 815, section e).
Next, when the relative speed of movement of the optical card 500 reaches the prescribed speed-v1, the MPU 512 applies a constant-speed pulse (voltage -V2) for maintaining this speed to the x direction drive motor 516 (step 816, section f), and the optical head 514 records or reproduces information to or from a desired track 504 of the optical card 500 (step 817, section f).
When the optical card 500 and optical head 514 assume a prescribed positional relationship, the MPU 512 applies a decelerating pulse (voltage V1) to the x direction drive motor 516, thereby decelerating the relative speed of movement of the optical card 500 (step 818, section g), and when the relative speed of movement of the optical card 500 reaches zero (YES at step 819, section h), it returns to step 802 and applies an accelerating pulse to the x direction drive motor 516 (step 802, section i).
These operations are repeated until the optical recording and reproduction device 510 has completed the prescribed recording and reproduction operations.
Furthermore, the track jump operation can be implemented during deceleration of the relative speed of movement, by a similar method.
In the first example of a conventional track jump operation described above, track jumping is implemented when the relative speed of movement between the optical card and optical head is constant. However, this constant state of the relative speed of movement corresponds to the timing at which the optical head scans the central region of the optical card, and since the optical card and optical head are moving at a high relative speed, the number of pits that can be formed in the central region of the optical card is reduced and consequently, a problem arises in that the amount of information that can be recorded onto the optical card is reduced.
Furthermore, in the second example of a conventional track jump operation, since track jumping is implemented when the relative speed of movement between the optical card and optical head is zero, in other words, when the optical head is scanning an end region of the optical card, the problem associated with the first example is resolved, but a further problem arises in that the relative speed of movement between the optical card and optical head must be held longer in a zero state in order to perform the track jump operation, and therefore the time required for recording or reproducing info is increased.
In the third example of a conventional track jump operation, since track jumping is implemented when the relative speed of movement between the optical card and the optical head is accelerating or decelerating, the optical head does not record or reproduce any information during this acceleration (or deceleration), and therefore there is no problem of reduced information recording capacity as in the first example, and it is also unnecessary to hold the relative speed of movement of the optical card and optical head at zero for a long period of time.
However, in the third example of a track Jump operation, due to the oscillation induced by acceleration or deceleration of the relative speed of movement between the optical card and optical head, a problem arises in that track jumping cannot be performed accurately and the device may jump incorrectly to a different information track from the desired information track.